radioactivity

radio active decay

- the process where an unstable atomic nucleus spontaneously transforms into a more stable one by releasing energy in the form of radiation, such as alpha, beta, or gamma particles

radioactivity

the emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei.

radioactve particle facts

some atoms are naturally radioactive/emit radiation

-radiation is emitted randomly from unstable nuclei and it decays to become more stable

-when a nuclei decays, it is changed

-The mass/energy/compostitio of the nucleus is changed and a radioactive particle is emitted.

what are alpha particles composed of

2 protons and 2 neutrons He

alpha mass

4

alpha charge

2

alpha penetrating power

skin or paper (weak)

alpha range in air

5-6cm

alpha ionizing ability

strongly ionizing

alpha use

becayse of their penetrating range and ionizing ability are ideal for detecting smoke

what are beta particles composed of

1 high energy electron 0

-1 e

beta mass

0

beta charge

-1

beta penetrating power

moderate

aluminum (a few mm thick)

beta range in air

1m (moderate)

beta ionizing ability

moderately ionizing

beta use

used for thickness monitoring bc it has enough penetrating power for thin materials

What is gamma composed of

gamma is a wave

e.g. 0

0 g

gamma mass

0

gamma charge

0

why does gamma have no mass or charge

because it is a form of high energy radiation, not a particle

gamma penetrating power

lead or concrete

gamma range in air

unlimited

gamma ionizing ability

weakly ionizing

gamma use

tracers because of their high penetrating power allows them to pass through the body to be detected outside. They are also weakly ionizing so wont mutate any cells whilst inside the body

why dosent the emmision of gamma rays change the atomic number (mass or charge) of a nucleus like alpha and beta.

because they have no mass or charge themselves

alpha behaviour in a magnetic field

affected but not much

beta behaviour in a magnetic field

the biggest reaction because its charge is bigger compared to its mass

gamma behaviour in a magnetic field

passes straight through bc no charge

units for radioactivity

bequerels - Bq

1Bq = 1 decay per second

(count rate also means decays per second)

units for radiation dose

sieverts - Sv

1000 mSv = 1 Sv

half life

the time taken for half the radioactive nuclei in a sample to decay

What is the curve called to show half-lives of a sample on a graph

exponential curve

radioactive contamin

the unwanted presence of materials containing radioactive particles

radioactive irradiation

The process of exposing an object to nuclear radiation

- dosent make a obkect radioactive

- used for sterilization because rays pass through killing bacteria and no trace left behind

how radiation can harm

- cataracts in the eye

- cancer

- infertility

- radiation burns on the skin

- damaged immune system

- vomiting

- internal bleeding

safely handling radioactive materials

- limit exposure time

- don't handle, use tongs

- wear protective clothing

background radiation - natural

50% radon gas from the ground

13% the ground

13% medical

13% cosmic rays

13% food and drink

background radiation - artificial

mostly medical

5% nuclear weapons

<2% other

radiotherapy

- irradiates the body to kill cancer cells

tracers

- gamma rays

- pass through the body

- least ionizing

- half-life, a few hours

nuclear fission

the process of splitting large unstable nuclei

where is controlled nuclear fission taken place

nuclear reactor

common substances used for nuclear fission

uranium-235 and plutonium-239 because they are large unstable nuclei

uk nuclear fission source

uranium-235 because it is naturaly occuring whereas in america plutonium-239 is naturally occuring

How to induce nuclear fission

fire a neutron at uranium-235. the nuclei will become unstable as uranium-236 and splits into 2 daughter nuclei releasing 3 neutrons and gamma radiation

daughter nuclei

they will be roughly the same size

energy produces from nuclear fission

mostly released as kinetic energy (due to fast moving neutrons and daughter nuclei) and energy in form of gamma radiation

chain reaction

-keeps going once started

-produces more and more energy

controlled nuclear fission

nuclear power station

uncontrolled nuclear fission

nuclear bomb

nuclear reactor/core

First a neutron strikes a uranium atom causing it to split, giving off 2 daughter nuclei, 3 neutrons and gamma radiation. the 2 daughter nuckei get another nuclei fired at them for more fission, the neutrons get absorbed by the control rods and the gamma radaiation is an exothermc reaction so the fuel rods heat up causing the water to turn into steam.

making electricity in a nuclear power station

-nuclear rods get hot by fission

-water turns to steam

-turbine turned by steam

-turbine turns generator

advantages of nuclear fission

no co2 produced

no noise

no burning

disadvantages of nuclear fission

non-renewable energy source

uranium and plutonium are expensive and hard to access

radioactive waste is produced!

disposing nuclear waste

nuclear waste is radioactive

has a long half-life so remains dangerous

stored underwater or underground for at least a year before being dealt with

stored in lead lined containers

nuclear fusion

The joining of two light nuclei to form a larger, bigger, heavier nucleus

e.g. 1 2 3

1 H + 1 H = 2 H

where does nuclear fusion occur naturally

sun/stars

energy from fusion

-fusion releases energy in the form of gamma radiation

-some form of energy that is released is due to the kinetic energy of the particles

-most of the energy from nuclear fusion is released as radiation

-when fusion occurs, some of the mass (particles) is converted into energy

e.g. e=mc^2 c=speed of light m=some of the mass to energy=e

fusion on earth - positives

-releases lots of energy

-hydrogen is plentiful and cheap

-hydrogen and helium are fairly safe

-almost no radioactive waste

-no riskof nuclear accident

-no co2 produced

fusion on earth - disadvantages

because the 2 light nuclei have the same charge, a force of replusion keeps the 2 hydrogen nuclei (protons) apart. In order for fusion to happen, very high temperatures are needed to force the two nuclei together. This means it is using more energy than it produces

a fusion reactor - 'tokamak'

At the moment, making fusion happen on earth si expensive and difficut, and uses more energy than it produces.